Ext JSON（JavaScript Object Notation）對(duì)象的字符串是一種輕量級(jí)的數(shù)據(jù)交換格式，常見于前端和后端之間的數(shù)據(jù)傳遞。通過(guò)使用JSON格式，可以將JavaScript對(duì)象轉(zhuǎn)換為字符串，并在需要時(shí)反轉(zhuǎn)換回來(lái)。

{
"name": "Tom",
"age": 25,
"interests": ["music", "sports", "reading"],
"address": {
"city": "Shanghai",
"district": "Pudong New Area",
"street": "Century Avenue"
}
}

以上是一個(gè)JSON對(duì)象的字符串表示。它由一個(gè)對(duì)象組成，對(duì)象的每個(gè)屬性都由名稱和值組成。其中，name和age是基本數(shù)據(jù)類型，interests是一個(gè)數(shù)組類型，address是一個(gè)嵌套對(duì)象類型。

在ExtJS中，可以使用Ext.JSON.encode()和Ext.JSON.decode()方法來(lái)進(jìn)行JSON對(duì)象和字符串之間的轉(zhuǎn)換。例如，以下代碼將一個(gè)JavaScript對(duì)象轉(zhuǎn)換為字符串：

var obj = {
name: "Lucy",
age: 20,
interests: ["dancing", "traveling"],
address: {
city: "Beijing",
district: "Chaoyang District",
street: "Gongti North Road"
}
};
var jsonString = Ext.JSON.encode(obj);
console.log(jsonString);

輸出結(jié)果為：

{"name":"Lucy","age":20,"interests":["dancing","traveling"],"address":{"city":"Beijing","district":"Chaoyang District","street":"Gongti North Road"}}

同樣地，以下代碼將一個(gè)JSON字符串轉(zhuǎn)換為JavaScript對(duì)象：

var jsonString = '{"name":"Jack","age":30,"interests":["photography","cooking"],"address":{"city":"Guangzhou","district":"Tianhe District","street":"Tianhe Road"}}';
var obj = Ext.JSON.decode(jsonString);
console.log(obj);

輸出結(jié)果為：

{
"name": "Jack",
"age": 30,
"interests": ["photography", "cooking"],
"address": {
"city": "Guangzhou",
"district": "Tianhe District",
"street": "Tianhe Road"
}
}

總結(jié)：Ext JSON對(duì)象的字符串是一種常見的數(shù)據(jù)交換格式，方便實(shí)現(xiàn)不同系統(tǒng)之間的數(shù)據(jù)傳遞。在ExtJS中，可以使用Ext.JSON.encode()和Ext.JSON.decode()方法來(lái)進(jìn)行JSON對(duì)象和字符串之間的轉(zhuǎn)換。